Capitalizing on a unique opportunity to build upon a recently funded (Epidemiologic Prevention Center for Early Risk Behaviors, NIMH 5 PO MH38725), short-term longitudinal study of an epidemiologically defined sample of 2,400 first grade children, this FIRST Award requests five years of support to accomplish the following aims: (1) To study the significance of depressive symptoms and the validity of Major Depressive Disorder [MDD, Diagnostic and Statistical Manual of Mental Disorders II - Revised (DSM-III-R), American Psychiatric Association (APA), 1987] in children between the ages of five and seven. To accomplish this aim, the following steps are proposed. First, data on the short and longer term stability of children's self-reported depressive symptoms will be examined. Second, the extent to which these symptoms covary in conformity with the DSM-III-R definition of MDD will be tested empirically. Third, the extent to which self-reported depressive symptoms exist in the absence of anxiety and withdrawal will be examined. Fourth, the degree of impairment in adaptive functioning associated with children's reports of depressive symptoms will be assessed. Fifth, as a means of externally validating children's self- reports of depressive symptoms, the relationship between children's self- reported depressive symptoms and direct observation of overt indicators of depression will be studied. Sixth, utilizing a multi-stage, nested case control design the relationship between self-reports of depressive symptoms and clinically diagnosed cases of MDD will be examined. Seventh, the interrater reliability for MDD will be assessed. Eighth, to test the specificity of MDD, the relationship between MDD and adaptive functioning will be examined controlling for the presence of comorbid symptoms and disorders. Ninth, the external correlates of MDD, including parental psychiatric history, will be contrasted with those of the childhood anxiety and disruptive oppositional disorders. (2) In addition to studying the significance of depressive symptoms and the validity of MDD in 5- to 7-year old children, the proposed research will seek to test a developmental epidemiological model of the complex interplay of child and family variables in the etiology and course of depressive symptoms and MDD. The data on etiology and course should facilitate the development of effective strategies for treating and preventing depressive symptoms and MDD in young children. (3) The data from this study will be used to support an R01 application to expand and extend this study into middle childhood and early adolescence.